Certain aircraft members are often electroplated. Electroplating a copper layer onto a graphite-epoxy composite member provides conductive paths into the fibers, thus creating a spark-free composite assembly. For example, electroplating a copper layer onto fuel tank supports and rotor mounts provides lightning strike protection.
Electroplating of graphite-epoxy composite members presents particular difficulties. A graphite-epoxy composite member is constructed of conductive graphite fibers bonded together by nonconductive epoxy and has a nonconductive epoxy outer layer. Electroplating directly onto a nonconductive material, such as epoxy, is not possible because electric current must flow through the plating fluid and into the surface being plated.
A further problem is that the composite members requiring electroplating have many different shapes. For example, the composite member may be a rib section inside the wing of an aircraft or an outside, aerodynamically shaped surface. Once the member is installed on the aircraft, the surface region to be electroplated may be positioned in any orientation, including vertical and inverted. In-situ electroplating of graphite-epoxy composite members therefor presents considerable difficulties.
A capsulation system for electroplating graphite-epoxy composite members is illustrated in commonly owned U.S. Pat. No. 4,750,981, to Dalland, et al., incorporated herein by reference. In the system of Dalland et al., custom shaped hard capsules are placed over the area to be plated. Plating fluid is placed inside the container and agitated with air bubbles.
U.S. Pat. No. 4,882,016 ('016), to Westerman, commonly owned and incorporated herein by reference, describes an in-situ surface treatment containment apparatus and method. As shown in the '016 patent, a treating chamber is formed from a flexible membrane and treating fluid is drawn into the flexible membrane by a vacuum. Unfortunately, the treating membrane collapses completely against the part and an insulating member thus preventing the space between the cathode and the part from being precisely controlled. Further, an electrically insulating member directly contacts the anode and the surface region, which is undesirable during electroplating.